The principal objective is to approach a satisfying understanding at the molecular level of oxidative and photosynthetic phosphorylation and of other related biological energy transductions. Experiments are designed to test a new concept that in oxidative phosphorylation ATP formed at the catalytic site by reversal of hydrolysis is liberated by an energylinked protein conformational change, and to assess the involvement of energy-linked conformational changes in active transport and muscle contraction. Approaches used will include rapid and sensitive measurements of the initial rate of 32Pi labeling of active-site ATP in mitochondria and chloroplast particles; correlated O18 exchange measurements to establish if the rapid cleavage and resynthesis of ATP at the catalytic site accounts for the exchanges; determination if the first phosphoryl acceptor is AMP or ADP; elucidation of the energy requirements for formation and release of bound ATP at the catalytic site; measurements of ATP binding in different energized states; determination of spatial arrangements and nearest neighbors of membrane proteins involved in ATP formation; fractionation of membranes with attempted preservation of energy-linked conformational changes and exchange reactions; development and application of probes of these conformation changes; correlated studies with active transport and myosin-ATPase; and attempted crystallization of mitochondrial and chloroplast ATPases for x-ray studies of subunit interrelationships.